The German MP40 (and its predecessor, the MP38) brought about several unique features that inspired many future small-arms designs after WWII, including a folding stock and parts extensively made from steel, aluminum and plastic.

The folding stock brought the MP40’s overall length down to just 24.8 inches, and its extensive use of sheet metal kept its unloaded weight to 8.75 pounds—much lighter than the American Thompson.

The MP40’s barrel and front sight feature shrouds to protect against careless handling. The triangular projection under the barrel ensured the muzzle safely cleared a vehicle’s window, for example.

The German MP40 worked well in urban settings. Here members of the SS hold a position in a townhouse in Warsaw, Poland, in August of 1944 during the “Warsaw Uprising.”

While the MP38 had an aluminum grip frame, the MP40’s (shown) was crafted from stamped steel. Also note the ribbed Bakelite grip panels.

Users could not lock the bolt closed on original MP40s, but a sheet-metal shroud was added to the charging handle to solve this problem.

The receiver was mostly made of stamped sheet metal, with an extra-wide ejection port on the right side for greater reliability.

The under-folding stock was fitted with an oblong, skeletonized buttplate that locked into place when fully extended.

Manufacturer markings can be found at the front of the receiver, just ahead of the mag well. Erma’s mark (shown) is an eagle perched on top of the numbers 280

The MP40 was designed to feed from 32-round stick magazines. Also note the round, checkered magazine release and the gripping lines along the side of the magazine well.

The MP40, or Maschinenpistole 40, was a turning point in submachine gun design and manufacture. Early submachine guns relied on heavy and expensive milled-steel components and featured bulky wooden stocks inspired by contemporary carbines. The MP40 pioneered the use of economical and lightweight materials such as aluminum, plastic and sheet-metal stampings. As Thomas Nelson observed in The World’s Submachine Guns, “The MP40…left a legacy in production techniques which are copied by practically every country to indulge in submachine gun production since the MP40 set the pace.” Although the MP40 was certainly revolutionary, it also benefitted from earlier German designs.

Toward the end of World War I, the German army pioneered the design, manufacture and use of the submachine gun. Trench warfare demonstrated the need for a compact, lightweight, rapid-firing gun that could serve as a “trench broom.” German trench raiders frequently expended six or seven times their planned allotment of grenades when clearing trenches and fortifications. The lack of appropriate firearms forced German trench raiders to desperate measures such as arming themselves with long-barreled Artillery Lugers fitted with shoulder stocks and carrying as many 32-round “snail drum” magazines as they could scrounge. Equipped this way, German troops used them as improvised rapid-fire semi-automatic carbines.

Although designers in almost every warring nation were working on appropriate firearms, the 9mm Luger MP18/I was the first submachine gun to reach the trenches in significant numbers. Designed by Hugo Schmeisser and built by Bergmann, approximately 35,000 were made before World War I ended in November 1918. The first MP18/Is were of course issued to assault troops, but the Germans planned to make them general issue once sufficient numbers were available.

Learning From Defeat

The folding stock brought the MP40’s overall length down to just 24.8 inches, and its extensive use of sheet metal kept its unloaded weight to 8.75 pounds—much lighter than the American Thompson.

There were not enough MP18/Is to change the outcome of the war for Germany, but it did help accelerate changes in small-unit tactics. And it certainly made an impression on the Allies, who ensured the Treaty of Versailles specifically prohibited the German army from having submachine guns.

The development and production of submachine guns continued, however, because German manufacturers found a rich market among domestic and foreign law enforcement agencies. As widespread social unrest throughout Europe followed in the wake of World War I, nothing was really done to curb the sale of firearms to German police and paramilitary units. This was because, as much as they did not want Germany to re-arm, the Allies didn’t want to see the country fall into the hands of communist revolutionaries.

Perhaps the most active and innovative German submachine gun manufacturer of the post-WWI era was Erma (Erfurt Maschinenfabrik). In fact, Erma specialized in submachine guns, and it was one of the few gun makers to do so, other than Auto-Ordnance, the U.S. firm founded by Colonel John Taliaferro Thompson. Erma’s design, manufacturing and management staff members were culled from workers let go from the defunct state arsenal at Erfurt.

When Hitler began re-arming Germany in the mid-1930s, one of his first priorities was the German army’s fledgling tank corps, or Panzertruppe. In addition to tanks, the armored troops needed specialized equipment, including small arms. In particular, they needed a firing-port weapon that could double as a submachine gun for the mechanized infantry that would accompany the tanks. Accordingly, the new submachine gun had to be compact enough to fit in the cramped confines of an armored vehicle. Naturally, the armored corps turned to Erma, whose designers created a simple design that incorporated many innovations, including a folding metal stock.

Earlier MP38

The German MP40 worked well in urban settings. Here members of the SS hold a position in a townhouse in Warsaw, Poland, in August of 1944 during the “Warsaw Uprising.”

Unfortunately for Erma and the new armored corps, the German army’s ordnance board, or Heereswaffenamt (HWA), caught wind of the new project and nixed it. At the time, German troops were equipped with a hodgepodge of submachine guns, with everyone including the new paratroops (Fallschirmjaeger) begging for a special design. If the HWA were going to approve a new submachine gun for the tank corps, it would have to satisfy the needs of other specialist troops as well.

The HWA recognized two main problems with the outdated designs in its inventory, such as the MP-28II, MP34 and the EMP. These models, like other first-generation submachine guns, were designed around wooden stocks that added a tremendous amount of unnecessary weight and bulk, which led to complaints from the paratroopers and tankers. Secondly, the guns were manufactured through traditional production methods such as milling and forging, which resulted in small arms that were well made and sturdy but far more expensive and time-consuming to produce than necessary.

The experience of Germany’s Condor Legion in the Spanish Civil War showed the German military leadership that the fluid, mechanized combat they advocated for the future made the need for fully automatic small arms more acute than ever. As a result, the HWA called on Bernhard Gaipaul, the director of Erma, to submit a submachine gun that could be mass-produced for use by the regular infantry and still meet the needs of the armored corps, paratroopers, police and other special units. Gaipaul presented Erma’s original design for the armored corps virtually unchanged, and it was quickly approved by the HWA and adopted as the Maschinenpistole 38, or MP38.